Many of today's electrical systems and equipment generate and emit electromagnetic wave energy during their operation. This emission of electromagnetic wave energy into the environment adversely affects the operation of other electrical or electronic systems, and equipment in the vicinity of the source of the emission. Accordingly, electromagnetic wave energy emitted from electrical or electronic systems and equipment is referred to as electromagnetic interference, or "EMI".
In an attempt to control EMI emissions, the Federal Communications Commission (FCC) has adopted a set of regulations that limit the maximum level of electromagnetic emissions from computing devices. The FCC definition of a computing device is intentionally broad to include electronic equipment used for computing, controlling, recording, storing and transferring information.
Controlling EMI emissions from a system is a complex matter which depends upon many factors. Accordingly, no one single solution exists. In electrical or electronic systems using printed circuit boards, it has been found that the printed circuit boards emit a substantial amount of EMI. Accordingly, there exist a need to develop new cost efficient ways to reduce the amount of EMI emitted by systems or equipment with printed circuit boards to a level below the maximum permissible level set by the FCC.
One example of a prior device for reducing EMI is disclosed in U.S. Pat. No. 4,991,062 to Nguyenngoc, the entire disclosure of which is hereby incorporated herein by reference. The Nguyenngoc device provides a housing with a plurality of printed circuit boards. Each of the printed circuit boards has an insulated faceplate with a metallic clip for shunting the open face of the bay. However, the Nguyenngoc device has the disadvantage, among others, that the clip on the faceplate must contact both the upper and lower designation strips for shunting across the open face of the bay to reduce EMI. Accordingly, the clip of Nguyenngoc may become permanently deformed after many insertions and withdrawals of the card. Thus, the clip will no longer provide a solid, positive electrical connection with the designation strips.
Some other examples of prior devices for reducing EMI are disclosed in the following U.S. Pat. Nos. 3,469,015 to Warren; 3,573,558 to Babcock; 4,301,494 to Jordan; 4,384,165 to Loving, Jr.; 4,386,388 to Beun; 4,631,641 to Brombal; 4,694,380 to Mallory et al; 4,713,633 to Saito; 4,744,006 to Duffield; 4,758,928 to Wierec; 4,762,966 to Kosanda; 4,780,570 to Chuck; 4,821,145 to Corfits; 4,829,432 to Hershberger et al; 4,872,212 to Roos; 4,903,170 to Finney et al; and 4,970,625 to Belanger et al.
This invention addresses the above mentioned needs in the art, along with other needs which will become apparent from the following disclosure.